ἄκαμπτον
From LSJ
Ubi idem et maximus et honestissimus amor est, aliquando praestat morte jungi, quam vita distrahi → Where indeed the greatest and most honourable love exists, it is much better to be joined by death, than separated by life.
Russian (Dvoretsky)
ἄκαμπτον: τό1) негнущаяся часть (δακτύλου Arst.);
2) непреклонность (πρός и εἴς τι Plut.).